In commercial container filling or packaging operations, the containers typically are moved by a conveying system at very high rates of speed. A concentrated lubricant may be diluted with water to form an aqueous dilute lubricant solution (i.e., dilution ratios of 100:1 to 500:1), and copious amounts of aqueous dilute lubricant solutions are typically applied to the conveyor or containers using spray or pumping equipment. These lubricant solutions permit high-speed operation of the conveyor and limit marring of the containers or labels. Conveyors that transport containers that are not contained in secondary packaging may be referred to as “container conveyors.”
In commercial filling operations, conveyors may also be used to transport secondary packaging. Secondary packaging refers to something that holds containers, for example crates and pallets. The secondary packaging may be fabricated from different types of materials including polymeric materials (polyethylene, polypropylene, polystryrene and acrylonitrile butadiene styrene (ABS)), cardboard, wood, and composite. Conveyors that transport containers are typically situated at about table height from the floor and may therefore be referred to as “table top conveyors,” whereas conveyors that transport secondary packaging with containers are often embedded in the floor may therefore be referred to as “in-floor” conveyors. There are numerous significant differences between container conveyors and secondary packaging conveyors. In the case of container conveyors, containers typically weighing up to about 4 kilograms are moved at moderate to very high rates of speed, up to about 100 meters per minute, by chains that have a flat surface on which the container rests. Secondary packaging conveyors transport much heavier loaded objects weighing from about 15 kilograms up to about 100 kilograms or more at lower speeds, usually less than 20 meters per minute. Secondary packaging conveyors usually have chain links with flat surfaces on which packages rest where the cross section of the flat surface of the conveyor is smaller than the cross section of the surface of the conveyed object and the conveyed objects are situated directly on chain links during transport. Generally, falling or jamming of containers is not a problem for secondary packaging conveyors because of the slower speeds and because containers are conveyed on or inside of secondary packaging.
The purpose of lubricating container conveyors and secondary packaging conveyors is different. For container conveyors, the containers are often standing still while the conveyor quickly moves underneath them. Containers moved by container conveyors frequently experience large accelerations and decelerations. For example, a conveyed package may make abrupt changes in direction or transition from mass flow (moving in columns that are up to 40 containers wide or more) to single file. Therefore, it is frequently the case that containers will make accelerations and decelerations of up to forty fold in moving from one section of the conveyor to another. Under conditions of stopped containers with conveyors moving underneath them or conditions of rapid accelerations and decelerations, containers may fall over, jam, or be pushed together with sufficient force so as to marred or damaged. Thus, the main purpose of the lubricant is to permit higher speed operation by minimizing the falling and jamming of containers, while lubricating the equipment per se is either not a consideration or is at most a secondary consideration. For secondary packaging conveyor lubrication, emphasis is on reducing energy requirements of motors, reducing overheating of motors, and extending the lifetime of parts including the moving chain.
Historically, lubrication for both container conveyors and secondary packaging conveyors has been accomplished by application of dilute aqueous solutions of surfactants using spray or pumping equipment. Use of dilute aqueous lubricants typically requires use of large amounts of water on the conveying line, which causes an unduly wet environment near the conveyor line. The presence of large amounts of water promotes the growth of microbes, and typically a preservative must be added to retard biological growth, which is costly and also environmentally unfriendly. Finally, dilution errors can occur, leading to variations and errors in concentration of the aqueous dilute lubricant solution.